The present invention relates generally to a method and system for operating a motor vehicle. More particularly, the invention relates to a controller-assisted method and system for starting a motor vehicle.
Conventional motor vehicle starting systems include so-called xe2x80x9cfour-positionxe2x80x9d ignition key switches having one or more OFF or xe2x80x9clockxe2x80x9d positions, an ACC (xe2x80x9caccessoriesxe2x80x9d) position, a RUN position, and a START position. With the exception of alarm systems, clocks and mobile phones, most onboard electrical systems and components are typically disabled when the ignition switch is in the OFF position. When in the ACC position, designated vehicle accessories, such as a radio, power windows and the like, are activated via the vehicle""s electrical system. When in the RUN position, typically all onboard electrical systems, including the vehicle""s powertrain control module, are activated.
Typically, in order to start or xe2x80x9ccrankxe2x80x9d the engine, a conventional ignition switch must be turned to the START position and held there until the engine is successfully started. However, if the key is not held in the START position for a long enough period of time, a spring mechanism provided inside the switch will force the key back to the RUN position thus removing power from the starter solenoid and disengaging the starter motor. Uneventful cranking often depends on an operator""s ability to properly turn and maintain the switch in the START position for a required period of time.
Early release of the ignition switch from the START position can result in undesirable operating states of the internal combustion engine, including for example misstarts and reverse running of the engine. Repeated misstarts for example may damage the vehicle starter and reduce its longevity, and also effect a customer""s satisfaction with the vehicle. Misstarts may also increase vehicle exhaust emissions during vehicle cold start conditions. To address such problems, three-position mechanical ignition switches have been developed to reduce the level of effort required by an operator to turn and maintain the ignition switch in the proper position. See for example U.S. Pat. No. 5,936,316 having a combined RUN/START and no integral return spring.
Conventional starting systems however are also characterized by crank delays inherent in the vehicle start-up process itself. These delays are especially noticeable in vehicles having passive anti-theft systems (PATS) wherein a certain amount of time is required for key verification. Depending on the algorithms used and the number of previously unsuccessful verification attempts, the overall vehicle crank delay time is increased. Add to this the time required for other start-up processes, such as fuel pump priming, and the overall crank delay time is further increased.
Accordingly, the inventors have recognized a need for an improved vehicle starting system that minimizes overall vehicle crank times and provides an improved xe2x80x9ctouchxe2x80x9d feel to the vehicle starting process.
The aforedescribed limitations of conventional automobile starting systems are substantially overcome by the present invention, in which a method is provided for crank-starting a motor vehicle having an internal combustion engine, an operator actuatable switch, an electric starter and a corresponding starter relay. The method includes the steps of coupling the starter relay to a first circuit during one or more crank operations and coupling the starter relay to a second circuit during the one or more crank operations. Preferably, the first circuit is coupled to the high-side of the starter relay and the second circuit is coupled to the low-side of the starter relay. Crank operations include for example fuel pump priming and vehicle key verification.
An advantage of the present invention is that the overall crank delay of a vehicle""s starting system can be minimized by providing both high-side and low-side control of the starter relay. For example, vehicle key verification can be performed simultaneously with other vehicle start-up functions such as fuel pump priming. The dual control strategy also serves to eliminate single point failures that may lead to inadvertent start-up of the vehicle.
The claimed invention has an additional advantage of improving the xe2x80x9cfeelxe2x80x9d of the engine start-up process by providing a xe2x80x9ctouchxe2x80x9d quality or sensitivity to a conventional vehicle ignition switch. This is realized both by a shorter crank delay time, and by controller logic that automatically triggers control of the crank process when the ignition switch is in the xe2x80x9cstartxe2x80x9d position. In accordance with the present invention, the electronic controller assumes control of the start-up functions even when the operator misstarts the vehicle by prematurely and unintentionally releasing the ignition switch. The operator however is still able to override the starting process by turning the ignition switch to the OFF or ACC positions. The present invention thus has the further advantage of improving customer satisfaction by minimizing misstart occurrences due to premature and unintentional disengagement of the ignition switch from the xe2x80x9cstartxe2x80x9d position.
Still further, by minimizing misstart occurrences, cold start emissions caused by manifold fuel loading are reduced. Also, by preventing re-engagement and over-engagement of the starter motor in accordance with the present invention, starter motor and flywheel longevity can be increased.
In a related aspect of the invention, a vehicle starting system is provided having a starter motor coupled to a battery via a starter relay and an operator actuatable ignition switch. The system includes a first control circuit coupled to a high-side of the starter relay, a second control circuit coupled to a low-side of the starter relay, and an electronic controller coupled to the first and second circuits for providing high-side and low-side control signals, respectively, to the first and second control circuits when the ignition switch is turned to the start position.
Further advantages, objects and features of the present invention will become apparent from the following detailed description of the invention taken in conjunction with the accompanying figures showing illustrative embodiments of the invention.